The present invention relates to a resin-bonded magnet useful for wide ranges of magnet applications such as various rotors, magnet rolls for electromagnetic developing-type printers and photocopiers, audio speakers, buzzers, attracting or magnetic field-generating magnets, which has a maximum energy product (BH)max at least equal to those of anisotropic, sintered ferrite magnets, improved magnetizability and/or heat resistance as compared with conventional resin-bonded rare earth magnets, as well as small unevenness in a surface magnetic flux density. The present invention also relates to a ferrite magnet powder and a compound both for such a resin-bonded magnet. The present invention further relates to a rotor and a magnet roll each constituted by such a resin-bonded magnet.
Recently R-Fe-N-H magnetic alloys including Sm2Fe17Nx(x=2-6) magnet materials (U.S. Pat. No. 5,186,766) have come to be used as magnet materials replacing resin-bonded rare earth magnets comprising an isotropic or anisotropic magnet powder containing an Nd2Fe14B intermetallic compound as a main phase which have poorer magnetizability and high irreversible loss of flux, a measure of heat resistance, which is evaluated by a permeance coefficient. Resin-bonded rare earth magnets comprising Sm2Fe17Nx, however are insufficient in heat resistance and magnetizability to satisfy the recent needs of smaller size and higher performance for magnet applications. Therefore, their improvements are desired.
WO 98/38654 (PCT/JP98/00764) discloses an anisotropic, resin-bonded magnet composed of a ferrite magnet powder containing a hexagonal ferrite as a main phase and having a composition comprising 1-13 atomic % of A (at least one element selected from the group consisting of Sr, Ba, Ca and Pb, Sr being indispensable), 0.05-10 atomic % of R (at least one element selected from the group consisting of rare earth elements including Y and Bi, La being indispensable), 80-95 atomic % of Fe, and 0.1-5 atomic % of M (Co or Co and Zn). An example of this anisotropic, resin-bonded magnet is a ferrite magnet powder having coercivity iHc of 4.31 kOe for anisotropic, resin-bonded magnet, which is produced by dry-pulverizing a calcined body having such a composition as to provide a final composition of Sr0.7La0.3Fe12xe2x88x927Co0.3O19 (0.2% by weight of SiO2 and 0.15% by weight of CaCO3 were added before calcining) by a vibration mill, and then annealing the pulverized material at 1,000xc2x0 C. for 5 minutes in the air. This anisotropic, resin-bonded magnet having (BH)max less than those of anisotropic, sintered ferrite magnets is not satisfactory for use as a substitute for anisotropic, sintered ferrite magnets.
Japanese Patent Laid-Open No. 60-223095 discloses a field magnet constituted by a resin-bonded magnet comprising predetermined proportions of a hard ferrite magnet powder and a rare earth element-cobalt magnet powder bonded by a binder resin, assembled into a magnetic field apparatus for bubble memory device having a temperature coefficient of magnetic flux density of xe2x88x920.03%/xc2x0C. to xe2x88x920.20%/xc2x0 C. Though this field magnet has a temperature coefficient of a magnetic flux density in the above range, it fails to have improved heat resistance, magnetizability and the like.
xe2x80x9cRare Metal News No. 1936xe2x80x9d issued on Feb. 8, 1999 describes that magnetic properties can be improved, for instance, to (BH)max of 4-5 MGOe corresponding to the level of anisotropic, sintered ferrite magnets, by mixing an anisotropic Sm-Fe-N magnet powder and a ferrite magnet powder at predetermined proportions. However, the above reference makes no specific mention of the composition of the ferrite magnet powder. Investigation by the inventors has revealed that when a conventional Smxe2x80x94Fexe2x80x94N magnet powder for resin-bonded magnets and usual ferrite magnet powder (e.g. Sr-ferrite magnet powder) are compounded at predetermined proportions and bonded with a binder resin, the resultant resin-bonded magnet has (BH)max of 3.3 MGOe or more, equal to or more than those of anisotropic, sintered ferrite magnets and improved magnetizability and/or heat resistance, which are important in practical applications of magnets, as well as improved uniformity in a surface magnetic flux density.
Accordingly, an object of the present invention is to provide a resin-bonded magnet having improved magnetizability and/or heat resistance as compared with those of conventional resin-bonded rare earth magnets and further small unevenness in a surface magnetic flux density.
Another object of the present invention is to provide a ferrite magnet powder and a compound both for such a resin-bonded magnet.
A further object of the present invention is to provide a rotor and a magnet roll each constituted by such a resin-bonded magnet.
The ferrite magnet powder for resin-bonded magnets according to the present invention comprises powder obtained by disintegrating a sintered ferrite magnetic material, the sintered ferrite magnet powder having a substantially magnetoplumbite-type crystal structure and a basic composition represented by the following general formula:
(A1xe2x88x92xRxe2x80x2x)O.n[(Fe1xe2x88x92yMy)2O3] by atomic ratio,
wherein A is Sr and/or Ba; Rxe2x80x2 is at least one selected from the group consisting of rare earth elements including Y, La being indispensable; M is Co or Co and Zn; and x, y and n are numbers meeting the following conditions:
0.01xe2x89xa6xxe2x89xa60.4,
0.005xe2x89xa6yxe2x89xa60.04, and
5.0xe2x89xa6nxe2x89xa66.4.
The sintered ferrite magnet powder preferably contains SiO2 and CaO in amounts of 0.05-0.55% by weight and 0.35-1% by weight, respectively, per 100% by weight of the sintered ferrite magnet powder, because such a ferrite magnet powder can provide a sintered body having a dense structure, which shows good magnetizability and/or heat resistance.
The sintered ferrite magnet powder preferably has an average particle size of 2-300 xcexcm, because such a ferrite magnet powder is suitable for molding in a magnetic field.
The compound for resin-bonded magnets according to the present invention is composed substantially of:
(a) an Rxe2x80x94Txe2x80x94N-based magnet powder having a basic composition of Rxcex1T100xe2x88x92xcex1xe2x88x92xcex2Nxcex2, wherein R is at least one selected from the group consisting of rare earth elements including Y; T is Fe or Fe and Co; and xcex1 and xcex2 satisfy 5xe2x89xa6xcex1xe2x89xa620 and 5xe2x89xa6xcex2xe2x89xa630 by atomic %,
(b) a ferrite magnetic powder for resin-bonded magnets comprising powder obtained by disintegrating a sintered ferrite magnetic material, said sintered ferrite magnetic powder having a substantially magnetoplumbite-type crystal structure and a basic composition represented by the following general formula:
(A1xe2x88x92xRxe2x80x2x)O.n[(Fe1xe2x88x92yMy)2O3] by atomic ratio,
xe2x80x83wherein A is Sr and/or Ba; Rxe2x80x2 is at least one selected from the group consisting of rare earth elements including Y, La being indispensable; M is Co or Co and Zn; and x, y and n are numbers meeting the following conditions:
0.01xe2x89xa6xxe2x89xa60.4,
0.005xe2x89xa6yxe2x89xa60.04, and
5.0xe2x89xa6nxe2x89xa66.4.
(c) a binder.
By mixing and kneading the Rxe2x80x94Txe2x80x94N-based magnet powder having an average particle size of 1-10 xcexcm, the ferrite magnet powder having an average particle size of 0.9-2 xcexcm (first ferrite magnet powder) and a binder at appropriate proportions, it is possible to obtain a compound capable of providing a resin-bonded magnet with good magnetizability and/or heat resistance.
By compounding and kneading, at appropriate proportions, the Rxe2x80x94Txe2x80x94N-based magnet powder having an average particle size of 110 xcexcm, the ferrite magnetic anisotropic, granulated powder (second ferrite magnet powder) and a binder, it is possible to obtain a compound capable of providing a resin-bonded magnet with good magnetizability and/or heat resistance and small unevenness in a surface magnetic flux density.
By mixing and kneading the Rxe2x80x94Txe2x80x94N-based magnet powder having an average particle size of 1-10 xcexcm, the ferrite magnet powder which is powder formed from an anisotropic, sintered ferrite magnet body (third ferrite magnet powder) and a binder at appropriate proportions, it is possible to obtain a compound capable of providing a resin-bonded magnet with good magnetizability and/or heat resistance and small unevenness in a surface magnetic flux density.
The resin-bonded magnet according to the present invention is composed substantially of:
(a) an Rxe2x80x94Txe2x80x94N-based magnet powder having a basic composition of Rxcex1T100xe2x88x92xcex1xe2x88x92xcex2Nxcex2, wherein R is at least one selected from the group consisting of rare earth elements including Y; T is Fe or Fe and Co; and xcex1 and xcex2 satisfy 5xe2x89xa6xcex1xe2x89xa620 and 5xe2x89xa6xcex2xe2x89xa630, respectively, by atomic %,
(b) a ferrite magnetic powder for resin-bonded magnets comprising powder obtained by disintegrating a sintered ferrite magnetic material, said sintered ferrite magnetic powder having a substantially magnetoplumbite-type crystal structure and a basic composition represented by the following general formula:
(A1xe2x88x92xRxe2x80x2x)O.n[( Fe1xe2x88x92yMy)2O3] by atomic ratio,
xe2x80x83wherein A is Sr and/or Ba; Rxe2x80x2 is at least one selected from the group consisting of rare earth elements including Y, La being indispensable; M is Co or Co and Zn; and x, y and n are numbers meeting the following conditions:
0.01xe2x89xa6xxe2x89xa60.4,
0.005xe2x89xa6yxe2x89xa60.04, and
5.0xe2x89xa6nxe2x89xa66.4.
(c) a binder.
By compounding and kneading, at appropriate proportions, the Rxe2x80x94Txe2x80x94N-based magnet powder having an average particle size of 1-10 xcexcm, the ferrite magnet powder having an average particle size of 0.9-2 xcexcm (first ferrite magnet powder) and a binder, and molding the resultant compound in a magnetic field, it is possible to obtain a resin-bonded magnet having good magnetizability and/or heat resistance.
By compounding and kneading, at appropriate proportions, the Rxe2x80x94Txe2x80x94N-based magnet powder having an average particle size of 1-10 xcexcm, the ferrite magnet powder which is an anisotropic, granulated powder (second ferrite magnet powder) and a binder, and molding the resultant compound in a magnetic field, it is possible to obtain a resin-bonded magnet with good magnetizability and/or heat resistance and small unevenness in a surface magnetic flux density.
By compounding and kneading, at appropriate proportions, the Rxe2x80x94Txe2x80x94N-based magnet powder having an average particle size of 1-10 xcexcm, the anisotropic, sintered ferrite magnet powder formed by pulverizing an anisotropic, sintered ferrite magnet body (third ferrite magnet powder) and a binder, and molding the resultant compound in a magnetic field, it is possible to obtain a resin-bonded magnet with good magnetizability and/or heat resistance and small unevenness in a surface magnetic flux density.
From the aspect of practicality, the resin-bonded magnet of the present invention preferably has a ring shape, a cylindrical shape or an arc-segment shape, and is particularly useful when provided with radial or polar anisotropy.
The rotor according to the present invention is constituted by a resin-bonded magnet composed substantially of:
(a) an Rxe2x80x94Txe2x80x94N-based magnet powder having a basic composition of Rxcex1T100xe2x88x92xcex1xe2x88x92xcex2Nxcex2, wherein R is at least one selected from the group consisting of rare earth elements including Y; T is Fe or Fe and Co; and xcex1 and xcex2 satisfy 5xe2x89xa6xcex1xe2x89xa620 and 5xe2x89xa6xcex2xe2x89xa630, respectively, by atomic %,
(b) a ferrite magnetic powder for resin-bonded magnets comprising powder obtained by disintegrating a sintered ferrite magnetic material, said sintered ferrite magnetic powder having a substantially magnetoplumbite-type crystal structure and a basic composition represented by the following general formula:
(A1xe2x88x92xRxe2x80x2x)O.n[(Fe1xe2x88x92yMy)2O3] by atomic ratio,
xe2x80x83wherein A is Sr and/or Ba; Rxe2x80x2 is at least one selected from the group consisting of rare earth elements including Y, La being indispensable; M is Co or Co and Zn; and x, y and n are numbers meeting the following conditions:
0.01xe2x89xa6xxe2x89xa60.4,
0.005xe2x89xa6yxe2x89xa60.04, and
5.0xe2x89xa6nxe2x89xa66.4.
(c) a binder.
The rotor of the present invention comprising the above resin-bonded magnet as a field magnet has improved heat resistance and higher efficiency owing to good magnetizability of the resin-bonded magnet as compared with rotors comprising conventional resin-bonded rare earth magnets.
The magnet roll according to the present invention is constituted by a resin-bonded magnet composed substantially of:
(a) an Rxe2x80x94Txe2x80x94N-based magnet powder having a basic composition of Rxcex1T100xe2x88x92xcex1xe2x88x92xcex2Nxcex2, wherein R is at least one selected from the group consisting of rare earth elements including Y; T is Fe or Fe and Co; and xcex1 and xcex2 satisfy 5xe2x89xa6xcex1xe2x89xa620 and 5xe2x89xa6xcex2xe2x89xa630, respectively, by atomic %,
(b) a ferrite magnetic powder for resin-bonded magnets comprising powder obtained by disintegrating a sintered ferrite magnetic material, said sintered ferrite magnetic powder having a substantially magnetoplumbite-type crystal structure and a basic composition represented by the following general formula:
(A1xe2x88x92xRxe2x80x2x)O.n[( Fe1xe2x88x92yMy)2O3] by atomic ratio,
xe2x80x83wherein A is Sr and/or Ba; Rxe2x80x2 is at least one selected from the group consisting of rare earth elements including Y, La being indispensable; M is Co or Co and Zn; and x, y and n are numbers meeting the following conditions:
0.01xe2x89xa6xxe2x89xa60.4,
0.005xe2x89xa6yxe2x89xa60.04, and
5.0xe2x89xa6nxe2x89xa66.4.
(c) a binder.
The magnet roll of the present invention comprising the above resin-bonded magnets at least at developing magnetic poles has a higher surface magnetic flux density owing to good magnetizability of the above resin-bonded magnet, thereby being able to produce very finer image, as compared with magnet rolls comprising conventional resin-bonded rare earth magnets.